Keen Smell. The catoblepas has advantage on Wisdom (Perception) checks that rely on smell.
Stench. Any creature other than a catoblepas that starts its turn within 10 feet of the catoblepas must succeed on a DC 16 Constitution saving throw or be poisoned until the start of the creature's next turn. On a successful saving throw, the creature is immune to the stench of any catoblepas for 1 hour.
Tail. Melee Weapon Attack: +7 to hit, reach 10 ft., one target. Hit:21 (5d6 + 4) bludgeoning damage, and the target must succeed on a DC 16 Constitution saving throw or be stunned until the start of the catoblepas's next turn.
Death Ray (Recharge 5–6). The catoblepas targets a creature that it can see within 30 feet of it. The target must make a DC 16 Constitution saving throw, taking 36 (8d8) necrotic damage on a failed save, or half as much damage on a successful one. If the saving throw fails by 5 or more, the target instead takes 64 necrotic damage. The target dies if reduced to 0 hit points by this ray.
The catoblepas is as loathsome as the vile swamplands in which it lives. Like such wastelands, this conglomeration of bloated buffalo, dinosaur, warthog, and hippopotamus parts has few redeeming qualities. Few travelers willingly traverse the territory of a catoblepas.